Natural killer (NK) cells and lymphokine-activated killer (LAK) cells have been implicated in immunosurveillance against tumor cells (Barlozzani et al. (1983) J. Immunol., 131, 1024; Rayner et al. (1985) Cancer, 55:1327. It has been reported that the systemic administration of autologous LAK cells to patients with advanced cancer is beneficial (Mule et al. (1986) Cancer Res., 46: 676). This process is tedious in that large numbers of cells are needed for each patient. Also, the treatment of cancer patients using LAK and interleakin-2 (IL-2) is accompanied by substantial toxicities (Rosenberg et al. (1987) N. Engl. J. Med., 316: 889).
It has been shown that monocytes interfere with the activation of LAK activity by IL-2 (Rosenberg et al. (1987) N. Engl. J. Med., 316: 889). L-Leucine methyl ester (LME) and L-phenylalanine methyl ester (PME) were shown to remove monocytes from human peripheral blood mononuclear cells (PBMC) (Thiele and Lipsky ( 1985 ) J. Immunol., 134: 786; Hoyer et al. (1986) Cancer Res., 46: 2834). However, LME also depleted NK activity and NK cells (Thiele and Lipsky (1985) J. Immunol., 134: 786; Hoyer et al. (1986) Cancer Res., 46: 2834) . We have shown that depletion of monocytes by PME allows generation of LAK cells by IL-2 at cell densities of 5.times.10.sup.6 /mL or higher (Leung (1987) Lymphokine Research, 6, Abstract #1718; U.S. Pat. No. 4,849,329 to Leung and Rinehart.
It has been reported that adherent LAK (A-LAK) cells are generated by adherence to plastic of 24-hr IL-2-activated, monocyte-depleted PBMC (Melder et al. (1988) Cancer Res., 48, 346). These cells are highly proliferative and cytotoxic and are enriched for LAK cells (Leu19.sup.+, LAK phenotype) and low in CD4.sup.+ (Leu3.sup.+) T lymphocytes.
In previous reports, monocytes were removed by their adherence to nylon-wool columns or by centrifugal elutriation in order to generate A-LAK cells (Melder et al. (1988) Cancer Res., 48: 346). These procedures monocyte removal are tedious and complicated. Some LAK cell precursors may also adhere to the nylon-wool columns. Therefore, we have employed PME (5 mM) as a single step for monocyte depletion. We were able to generate A-LAK from PME-treated cells (copending, coassigned U.S. patent application Ser. No. 07/384,134, filed Jul. 21, 1989). Partial depletion of monocytes using lower concentrations (1 to 2.5 mM) of PME allowed more A-LAK cell expansion than did complete monocyte depletion using higher concentrations of PME.
IL-2 is a potent stimulator of NK cells and T cells. On the other hand, IL-4 was first described as a B cell growth factor (Howard et al. (1982) J. Exp. Med. 155: 914). IL-4 is considered as a lymphokine with multiple effects on B cells, T cells, NK cells, and monocytes (Widmer et al. (1987) J. Exp. Med. 166: 1447; Mitchell et al. (1989) J. Immunol. 142: 1548; Spits et al. (1987) J. Immunol. 139: 1142; Nagler et al. (1988) J. Immunol. 141: 2349; te Velde et al. (1989) Agents and Actions 26: 1; Spits et al. (1988) J. Immunol. 141: 29; Spits et al. (1988) J. Immunol. 141: 29; Brooks and Rees, (1988) Clin. Exp. Immunol. 74: 162; Kawakami et al. (1989) J. Immunol. 142: 3452). IL-4 alone cannot generate LAK activity from PBMC but can enhance specific CTL generation. IL-4 inhibited LAK induction by IL-2 but enhanced CTL induction by IL-2 (Spits et al. (1988) J. Immunol. 141:29; Brooks and Rees, (1988) Clin. Exp. Immunol. 74:162). More recently, it was reported that IL-4 enhanced cellular proliferation of IL-2-activated cells (Kawakami et al. (1989) J. Immunol. 142: 3452).
T lymphocytes that are positive for CD4 antigen are termed T helper/inducer cells. These CD4.sup.+ T cells are important for immunoregulation of immune functions. IL-2 is a potent stimulator of NK cells and T cells. IL-4 is considered as a lymphokine with multiple effects on B cells, T cells, NK cells, and monocytes. IL-4 enhances both CD4.sup.+ and CD8.sup.+ T cells to proliferate in response to mitogens. Therefore, the effect of IL-4 on T cells is not specific.